"I have collected several witness accounts from reliable people. In particular, in the Buslim neighborhood, due to the bombardments, a civilian building collapsed, causing the death of 40 people," he told Fides, the news agency of the Vatican missionary arm.

Libyan officials have taken foreign reporters to the sites of what they say were the aftermath of western air strikes on Tripoli but evidence of civilian casualties have been inconclusive.

Western powers say they have no confirmed evidence of civilian casualties.

Also on Thursday, British Foriegn Secretary William Hague said the defection of Libya's former Foreign Secretary Moussa Koussa to Britain would encourage others close to Muammar Gaddafi to abandon the Libyan leader.

He said Koussa, who flew into a British military airbase on Thursday, had not been offered any immunity from British or international prosecution and was voluntarily talking to British officials.

"Gaddafi must be asking himself who will be the next to abandon him," Hague told a news conference.